Wire rope for running wire

ABSTRACT

In a rope of a type of filling a resin constituting other member between strands, there is provided a wire rope for a running wire capable of promoting fatigue life by reducing a wire breakage at a point of being contacted to a core rope by precisely constraining a movement of a wire and reducing an elongation. 
     A rope having a core rope and a plurality of pieces of side strands arranged at an outer periphery thereof and twisted together, and a resinous spacer interposed between the side strands, in which the core rope includes a rope main body and a resin coating layer outwardly surrounding the core rope main body, the core rope main body and the side strand are separated by the resin coating layer, and the resin spacer is provided with a contour in correspondence with an outer layer wire of the side strand and invades between the wires.

TECHNICAL FIELD

The present invention relates to an improvement in a wire rope for a running wire.

BACKGROUND ART

re are very many kinds of wire ropes and it is well known that when a wire rope is used, unless a wire rope adapted to an object thereof and a place of use is selected, an advantage provided to a wire rope cannot sufficiently be utilized.

Particularly, a wire rope for a running wire in a crane or the like is bent by a sheave and is wound to a drum, and therefore, a fatigue resistance characteristic is requested.

In a background art, according to a rope of this kind, as shown by FIG. 1, there is adopted a structure of arranging a plurality of pieces of side strands ST at an outer periphery of a core rope CR to be twisted, and a fiber core or a metal core is used for the core rope. However, according to the structure, metal contact is unavoidable between the strands, between a sheave portion and the rope and disconnection by wear is brought about.

Although a number of prior arts have been proposed as a countermeasure thereagainst, problems are posed by the respective prior arts and the prior arts cannot be regarded as sufficient yet.

According to Japanese Patent No. 2876140 (Prior Art 1), a core rope is thinly coated with a resin, and there poses a problem that although disconnection by wear between the core rope and a side strand can be avoided, disconnection by wear between strands and at a contact face with a sheave cannot be avoided.

It is described in Japanese Patent No. 3493248 (Prior Art 2) that a spacer made of a resin is provided between side strands and an angle of an apex of the spacer is 60 degrees in an outer peripheral direction. However according to the prior art, a base end portion of the spacer is formed by a wedge-like shape, the wedge portion reaches a center of the rope, and therefore, an effective sectional area of the rope is reduced to pose a problem that it is difficult to use the rope for a use requesting a high breaking load.

JP-B-63-46196 (Prior Art 3) discloses that a filling member forming a diverging portion by way of a constriction by constituting a front end thereof in a fan-like shape is interposed between side strands. However, according to the prior art, a reinforcement core is put to a filling material, and therefore, there poses a problem that the filling material is not filled between wires constituting the side strand, further, when the reinforcement core is disconnected at an early stage, there is a possibility of bringing about a trouble by jumping out the reinforcement core from the filling material, further, since the reinforcement core is put to the filling material, a special equipment is needed for fabrication thereof to increase cost.

U.S. Pat. No. 6,360,522 (Prior Art 4) discloses that similar to Prior Art 3, a spacer formed with a diverging portion by way of a constriction by constituting a front end by a fan-like shape is oriented between side strands. However, also in the prior art, a resin having a high strength of a biaxially oriented molecular structure or the like is used, and therefore, the spacer is difficult to be deformed and is not filled between wires constituting a side strand, and therefore, there poses a problem that the wire is moved and a wire breakage at a point of being contracted to a core rope cannot be restrained and elongation of the rope is increased.

DISCLOSURE OF THE INVENTION

The invention has been carried out in order to resolve the above-described problem and it is an object thereof to provide a wire rope for a running wire capable of promoting fatigue life by reducing a wire breakage at a point of being contracted to a core rope by precisely constraining a movement of a wire in a rope of a type filled with a resin fabricated as other member between strands and reducing an elongation thereof.

In order to achieve the above-described object, the invention is characterized in a rope having a core rope and a plurality of pieces of side strands arranged at an outer periphery thereof to be twisted together therewith, and a resinous spacer interposed between the side strands, wherein the core rope includes a core rope main body and a resin coating layer outwardly surrounding the core rope main body, the core rope main body and the side strand are separated from each other by the resin coating layer, and the resin spacer is provided with a contour in correspondence with an outer layer wire of the side strand and invades between the outer layer side wires.

According to the invention, the core rope includes the core rope main body and the resin coating layer outwardly surrounding the core rope main body, the core rope main body and the side strand are separated from each other by the resin coating layer, and therefore, metal contact between the side strand and the core rope is prevented, and a wire breakage at a point of being contacted to the core rope can considerably be reduced. Further, by interposing the resin spacer between the strands, contact between the strands is prevented, a wire breakage at a valley of a rope between respective strands is prevented, a face pressure of a surface of the rope is reduced by increasing a portion thereof in contact with the sheave and service life in view of a wire breakage at a crown of the strand contacted to the sheave by wear can considerably be prolonged. Further, the resin spacer is provided with the contour in correspondence with the outer layer wire of the side strand and invades up to between the outer layer wires, and therefore, the movement of the wire is constrained, an excellent effect of capable of reducing the wire breakage at the point of being contacted to the core rope and capable of reducing an elongation of the rope is achieved.

According to a preferable embodiment of the invention, the resin spacer invades between the wires by a filling rate equal to or larger than 50%. Further preferably, the filling rate is equal to or larger than 60%. Here, filling rate=area (A) of the resin invading between the wires/area (B) of a gap between a circumcircle of the strand and an outermost layer wire×100.

According thereto, a degree of invasion of the resin to between the wires is high, and therefore, the movement of the wire can firmly be fixed, when the rope is bent by the sheave, the movement of the wire is firmly restrained, the wire breakage at the point of being contacted to the core rope is very inconsiderable, and the life is promoted. Further, the elongation can be reduced.

Preferably, the resin spacer comprises a streak member constituted by subjecting a thermoplastic resin selected from any of polypropylene species, polyethylene species, acrylic species, polyurethane species to extrusion molding, the streak member is provided with a sectional shape in which a head portion enlarged in a fan-like shape and a base portion in a fan-like shape smaller than the head portion are made to be continuous by a constriction edge, and a thickness among the constriction edges is constituted by a value increasing a gap of arranging the side strands on layer cores by 15 through 30%, that is, when the gap of arranging the side strands is constituted by 100, the thickness becomes 115 through 130%.

According to the constitution, the streak member is firmly plastically deformed by being compressed from an outer periphery thereof in a state of being arranged between the strands to thereby enable to form a state in which the resin spacer is filled between the wires to bite the wires. That is, the state of filling the resin spacer signifies that the resin spacer is provided with a press-fit filling portion exceeding the circumcircle of the side strands to bite the gap between the outer layer side wires at a side edge portion thereof, and the press-fit filling portion is constituted by a converging mountain shape on a front side of a bent portion along a contour of the outer layer side wire.

Thereby, the movement of the wire when the rope is bent is firmly restrained, the wire breakage at the point of being contacted to the core rope is very inconsiderable, further, the elongation can be reduced.

Although other features and advantages of the invention will become apparent by the following detailed explanation and a description of the drawings, the invention is not limited to a constitution shown in the embodiment so far as a basic characteristic of the invention is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a wire rope for a running wire of a background art.

FIG. 2-A is a sectional view showing an embodiment of a wire rope for a running wire according to the invention.

FIG. 2-B is a partially enlarged view of FIG. 2-A.

FIG. 3-A schematically shows an interwire resin filling rate according to the invention and is a sectional view of a state of filling a resin among wires.

FIG. 3-B is a sectional view showing a gap between a circumcircle of a strand and a wire of the outermost layer.

FIG. 4-A is an enlarged sectional view showing an example of a resin spacer before being filled among wires.

FIG. 4-B is a schematic view showing a relationship between a gap between wires and a size of a resin spacer.

FIG. 5 is an explanatory view showing a step and an apparatus of closing a rope according to the invention.

FIG. 6 is a sectional view showing a shape of a resin spacer after closing.

FIG. 7 is a sectional view showing another embodiment of the invention in which a side strand is schematically shown by a circular shape.

FIG. 8 is an explanatory view of equipment used for a fatigue test.

FIG. 9 is a diagram showing a result of a fatigue test of a rope according to the invention and a compared rope.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the invention will be explained in reference to the attached drawings as follows.

FIGS. 2-A, B and FIGS. 3-A, B show an embodiment of a wire rope for a running wire according to the invention, which is constituted by a core rope 1, a plurality of pieces of side strands 2, and a resin spacer 3 interposed between the strands 2.

The core rope 1 is provided with a resin coating layer 1 b to incorporate a core rope main body 1 a constituted by twisting steel wires or strands. The core rope 1 is constituted to be larger than an outer diameter of the side strand 2.

Although a structure of the core rope main body is arbitrary, according to the example, the core rope main body comprises IWRC of 7×7 in which at a surrounding of a core member 100 of 1×7 structure, 6 pieces of side members 101 having the same structure are arranged to twist. The resin coating layer 1 b is provided with a thickness sufficiently exceeding a circumcircle of the core rope main body 1 a in order to prevent the side strand 2 and the core rope main body 1 a from being brought into direct contact with each other. Although the resin coating layer 1 b is constituted by a circular shape in this example, depending on cases, in order to improve to settle the side strand, a spiral groove having a pitch equal to a pitch of twisting a rope may be provided at an outer periphery thereof. It is preferable that the spiral groove is provided with a depth and a width capable of making at least 1 piece of a wire at an outer layer of the side strand 2 falls thereinto.

A plurality of pieces (6 pieces in the drawing) of the side strands 2 are used. Although a structure of each side strand 2 is arbitrary, according to the example, the side strand 2 is constituted by a structure of 6×Fi (29). That is, the side strands 2 is constituted by a mode in which 7 pieces of relatively slender wires are arranged at a surrounding of a core wire, a total of 7 pieces of slender diameter wires are arranged at respective valleys between the slender wires to twist to constitute the inner layer and 14 pieces of outer layer side wires 201 are arranged to twist at a surrounding thereof.

Steel wires are used for the respective wires of the core rope 1 and the side strand 2. When a high strength is requested for a rope, a steel wire having a characteristic of a tensile strength of 240 kg/cm² or higher is used. Such a steel wire is provided by drawing a raw material wire having a carbon content equal to or larger than 0.70 wt %. The wire includes a wire having a thin corrosion resistant coating, for example, zinc plating, zinc/aluminum alloy plating or the like at a surface thereof. A diameter of the wire is selected to be able to deal with a fatigue by repeated bending by a sheave.

The respective side strands 2 are arranged at equal intervals at an outer periphery of the resin coating layer 1 b of the core rope 1, the resin spacers 3 are inserted to respective intervals of the respective side strands 2 and twisted together along with the side strands 2.

A streak member produced by extruding a thermoplastic resin is used for the resin spacer 3. Although polypropylene, polyethylene are general for a thermoplastic resin, a thermoplastic resin which is provided with a pertinent elasticity for adjusting a friction coefficient between the thermoplastic resin and a sheave and having a comparatively high friction coefficient and is not hydrolyzed in addition to wear resistance, weather resistance, flexibility (stress crack resistance), for example, acrylic species, polyurethane species (ether spices polyurethane or elastomer thereof) or the like is also preferable.

Further, a resin of the resin coating layer 1 b of the core rope 1 can use a resin having an excellent adherence with a core rope main body 1 a of polyvinyl chloride, nylon, polyester, polyethylene, polypropylene and copolymers of the resins. However, as a total of the rope, it is preferable that resins are the same or similar in physical, chemical properties, and therefore, it is preferable that the resin of the resin coating layer 1 b is the same as or similar to the resin of the resin spacer 3.

As shown by FIG. 4-A, the resin spacer 3 is provided with a head portion 3 a enlarged in a fan-like shape and a base portion 3 b in a fan-like shape smaller than the head portion and these are made to be continuous by constriction edges 3 c, 3 c in a state of a single member thereof.

As shown by FIG. 4-B, the resin spacer 3 is provided with a sectional area a′ pertinently larger than a sectional area a of an interval between the side strands 2. This is realized specifically by constituting a thickness between the constriction edges 3 c, 3 c by value constituted by increasing a gap of arranging the side strands on a layer center by, for example, 15 though 30%.

The resin spacers 3 are inserted to respective intervals of the respective side strands 2 and twisted together along with the side strands 2. A radius of curvature top face 300 of the head portion 3 a of the resin spacer 3 substantially coincides with a circumcircle of the rope, and a radius of curvature bottom face 301 is brought into close contact with the resin coating layer 1 b of the core rope 1.

As show by FIG. 2-B, the resin spacer 3 in the state of being twisted together includes a press-fit filling portion 30 exceeding the circumcircle of the side strand 2 and biting a gap between the respective outer layer side wires 201, 201, to constitute a converging mountain shape on a front side of a bent portion along a contour of the outer layer side wire 201 at a side edge portion thereof.

Here, a size of the press-fit filling portion 30 is expressed by a filling rate. As shown schematically in FIG. 3-A, when an area of the press-fit filling portion 30 invading between the outer layer side wires 201, 201 is designated by notation A, and an area of a gap S between the circumcircle of the side strands 2 and the outer layer side wires 201, 201 is designated by notation B, the filling rate is defined as A/B×100 (%).

According to the invention, the interwire filling rate is made to be equal to or larger than 50%, preferably, equal to or larger than 60%. The reason is that when the interwire filling rate is less than 50%, the wire 201 is fixed incompletely, when the rope is wound around a sheave, a movement of the wire 201 cannot firmly be restrained, and therefore, disconnection, particularly a wire breakage at a point of being contacted to a core rope cannot sufficiently be reduced. Further, because a force of constraining the wire is small, and elongation of the rope cannot sufficiently be reduced. Further, an upper limit of the interwire filling rate is about 99%.

A structure of the core rope main body 1 a, a structure of the side strand 2 are not particularly limited. The core rope main body 1 a may be constituted by IWRC of 7×7, the side strand 2 may be constituted by a structure of S (19), a total of the rope may be constituted by IWRC 8×S×(19), the core rope main body 1 a and the side strand may be constituted by 1×7 structure and the total of the rope may be constituted by 7×7 structure.

Explaining a method of fabricating the wire rope of the embodiment, the core rope 1 having the resin coating layer 1 b is fabricated by continuously passing the core rope main body 1 a through a resin extruder. Further, a necessary number of pieces of the side strands 2 are fabricated. On the other hand, the resin spacer 3 having the sectional area larger than the gap between the side strands 2, 2 is fabricated as described above by an extruding mold machine.

Next, these are twisted together into a rope in closing as shown by FIG. 5. In FIG. 5, numeral 5 designates a reel out portion, a bobbin 50 wound with the core rope 1 is arranged at a center portion and bobbins 51 wound with the side strands 2 are arranged on outer sides. A pipe shaft 6 is extended from the reel out portion 5 in a downstream direction, a horn 7 is rotatably mounted thereto, the horn is arranged with bobbins 71 wound with the resin spacer 3.

An end cover 8 is fixed to a vicinity of a front end of the pipe shaft 6, the end cover 8 is provided with a hole for inserting the core rope 1 at a center thereof, holes of inserting the side strands 2 and holes for inserting the resin spacer 3 are alternately provided at equal intervals at an outer periphery thereof. Further, a vise 9 for exerting a compression force from a radius direction is disposed on a downstream side of the end cover 8.

When the core rope 1, the side strands 2 and the resin spacer 3 are passed through the end cover 8 while rotating the end cover 8 to be guided to the vise 9, the respective side strands 2, 2 are arranged at the outer periphery of the resin coating layer 1 b, the resin spacers 3 are inserted to between the side strands 2, 2 and are fixed together with the rope while maintaining the state.

Further, since the vise 9 exerts the compression force to the rope in the radius direction, not only the resin spacer 3 having the sectional area larger than the gap between the side strands 2, 2 intentionally is brought into contact with the circumcircles of the respective side strands 2, 2, but also an extraneous amount of the sectional area is made to flow to between the outer layer side wires 201, 201 of the side strand 2 as shown by FIG. 3-A by plastic deformation and cured under the state to constitute the press-fit filling portion 30.

According to the rope provided in this way, in view of a relationship in which the core rope 1 is provided with the resin coating layer 1 b, a diameter of the core rope 1 is increased by that amount, the gap between the side strands 2 is easy to be formed and further, the side strand 2 and the core rope 1 are substantially separated by the resin coating layer 1 b. Therefore, metal contact between the side strands 2 and the core rope 1 is prevented and the wire breakage at the point of being contacted to the core rope is considerably reduced.

Further, the resin spacer 3 is interposed between the side strands 2, the side strands 2 are completely separated, and therefore, contact between the strands is prevented, and a wire breakage at a valley of the rope between the respective strands is prevented. The base portion 3 b of the resin spacer 3 is disposed up to the resin coating layer 1 b of the core rope 1 and does not reach the rope core, and therefore, also a steel member filling rate can be increased, and the rope strength can be improved. The outer face of the resin spacer 3 substantially coincides with the circumcircle of the rope, and therefore, a face pressure of the surface of the rope is reduced. Service life in view of a wire breakage at a crown of the strand contracted to the sheave can be prolonged.

Further, the resin spacer 3 is not only interposed between the side strands but also bites the gap between the wires 201, 201 constituting the outermost layer of the side strand 2 to fill the gap by the resin, brought into contact with the wires 201 under the state and is provided with a large resistance against a shift. Therefore, the movement of the wire 201 is restrained, and therefore, the wire breakage at a point of being contracted to the core rope is reduced.

FIG. 7 shows a second embodiment of the invention, according to the embodiment, the base portion 3 b of the resin spacer 3 is provided with a trapezoidal portion 3 d, and a resin layer is formed between the circumcircle of the side strand 2 and the resin coating layer 1 b of the core rope 1 by the trapezoidal portion 3 d. According thereto, the metal contact between the side strand 2 and the core rope 1 is further firmly prevented.

The other constitution is similar to that of the first embodiment, and therefore, the explanation of the first embodiment will be applied thereto.

EXAMPLES

There is fabricated a rope having a structure of IWRC 6×Fi (29) shown in FIG. 2-A, having 0/0, diameter 16 mm, a tensile strength 173kN. There is used a core rope having a diameter 7.5 mm coated with polypropylene resin by an extruding mold machine at an outer periphery of a core rope main body. 6 pieces of side strands having a diameter of 5.01 mm are used.

As a resin spacer, there is used a streak member constituted by subjecting polypropylene resin to extrusion molding. The resin spacer is provided with a sectional shape shown in FIG. 4-A, and when a gap of arranging wire cores of the side strands is constituted by 100, a thickness thereof is constituted by a dimension of 125% thereof. The resin spacer is inserted between the side strands by the method of FIG. 5 and is plastically deformed by exerting a compression force in a radius direction by a vise. In order to investigate a preferable condition, a radius direction compression degree is changed by variously constituting an inner diameter of the vise to provide ropes of examples 1 through 4 having the interwire filling rates of 10%, 35%, 60% and 95%.

There is carried out a fatigue test for endlessly connecting the examples 1 through 4, and winding the examples 1 through 4 around a drive sheave and a ram side sheave by way of two test sheaves having U grooves middle phases of which are shifted from each other by 30 cm and reciprocating the examples 1 through 4 as shown by FIG. 8. In a diameter D of the test sheave and a rope diameter d, it is constituted that D/d=20, SF=6 (28.8 kN).

For comparison, the fatigue test is carried out under the condition also with regard to a rope shown in FIG. 1 (comparative example 1) and a rope constituted by arranging and twisting side strands around the coated core rope (comparative example 2), and a relationship between a cycle number and a number of disconnection at interval of 1 pitch is investigated.

A result is as shown by FIG. 9, service life of example 1 through 4 interposed with the resin spacer 3 is longer than that of comparative examples 1, 2. The result is derived from a reduction in the wire breakage at a crown of the strand contacted to the sheave, and it is known that a very excellent result is achieved particularly when the interwire filling rate is equal to or larger than 60%.

Next, a situation of disconnection at respective portions is investigated by disassembling the respective ropes. A result thereof is shown in Table 1.

TABLE 1 strand core rope sample cycle mountain valley contact IWRC comparative example {circle around (1)} 1.7 × 104 times 11 15 65 82 comparative example {circle around (2)} 2.0 × 104 times 20 5 15 4 invented example 1 10% 2.2 × 104 times 29 0 33 8 invented example 2 35% 2.2 × 104 times 27 0 32 4 invented example 3 60% 2.5 × 104 times 28 0 10 6 invented example 4 98% 2.7 × 104 times 35 0 3 5

In view of Table 1, the comparative example 2 is provided with the resin coating at the core rope, and therefore, the wire breakage at the point of being contacted to the core rope is inconsiderable in comparison with comparative example 1 and also disconnection of the core rope main body is inconsiderable. However, the wire breakage at the valley of the rope between respective strands is considerable. In contrast thereto, when the interwire filling rate is increased by using the resin spacer, the cycle number is increased and the wire breakage at the valley of the rope to respective strands and the wire breakage at the point of being contacted to the core rope are considerably reduced. This is because the movement of the wire is fixed by press-fitting the resin between the wires, and therefore, the movement of the wire when bent by the sheave is effectively restrained.

Next, Table 2 shows a result of measuring elongation (%) for respective ropes.

TABLE 2 cycle comparative example invented example (time) {circle around (1)} {circle around (2)} 10% 35% 60% 98% 17000 0.5 0.3 0.35 0.28 0.19 0.16 20000 — 0.33 0.38 0.32 0.23 0.17 22000 — — 0.42 0.35 0.25 0.2 27000 — — — — — 0.23

As is apparent from the result, when the interwire filling rate is increased by using the resin spacer, the elongation is reduced, which can be regarded as the pertinent property for a rope used in a materials handling equipment of a crane or the like. 

1. A wire rope for a running wire characterized in a rope having a core rope and a plurality of pieces of side strands arranged at an outer periphery thereof to be twisted together therewith, and a resinous spacer interposed between the side strands, wherein the core rope includes a core rope main body and a resin coating layer outwardly surrounding the core rope main body, the core rope main body and the side strand are separated from each other by the resin coating layer, and the resin spacer is provided with a contour in correspondence with an outer layer wire of the side strand and invades between the outer layer side wires.
 2. The wire rope for a running wire according to claim 1, wherein the resin spacer comprises a streak member constituted by subjecting a thermoplastic resin selected from any of polypropylene species, polyethylene species, acrylic species, polyurethane species to extrusion molding, the streak member is provided with a sectional shape in which a head portion enlarged in a fan-like shape and a base portion in a fan-like shape smaller than the head portion are made to be continuous by a constriction edge, and a thickness among the constriction edges is constituted by a value increasing a gap of arranging the side strands on layer cores by 15 through 30%.
 3. The wire rope for a running wire according to claim 1, wherein the resin spacer invades between the wires by a filling rate equal to or larger than 50%, the resin spacer includes a press-fit filling portion biting a gap between respective outer layer side wires by exceeding a circumcircle of the side strands at a side edge portion thereof, and the press-fit filling portion constitutes a converging mountain portion on a front side of a bent portion along a contour of the outer layer side wire.
 4. In the wire rope for a running wire according to claim 1, the wire rope is fabricated by being processed by following steps. 1) A step of fabricating the core rope having the resin coating layer by continuously passing the core rope main body through a resin extruding machine, on the other hand, fabricating the resin spacer having a sectional area larger than a gap between the side strands by an extruding mold machine. 2) A step of arranging the respective side strands at an outer periphery of the resin coating layer of the core rope, inserting the resin spacer between the side strands and twisting together the respective strands and the core rope and the resin spacers into a rope under the state. 3) A step of forming the press-fit filling portion by exerting a compression force to the twisted rope from a radius direction to thereby bring the resin spacer having the sectional area larger than the gap between the side strands into contact with the circumcircle of the respective side strands, making an extraneous amount of the sectional area flow to between the outer layer side wires of the side strands by plastically deforming the extraneous amount of the sectional area and curing the resin spacer under the state. 